Contexts created with vm.createContext() do not define the URL() constructor

<!-- Thank you for reporting a possible bug in Node.js. Please fill in as much of the template below as you can. Version: output of `node -v` Platform: output of `uname -a` (UNIX), or version and 32 or 64-bit (Windows) Subsystem: if known, please specify the affected core module name If possible, please provide code that demonstrates the problem, keeping it as simple and free of external dependencies as you can. --> * **Version**: v12.6.0 (also seen in 10.13.0) * **Platform**: Darwin Davids-MacBook-Pro.local 18.5.0 Darwin Kernel Version 18.5.0: Mon Mar 11 20:40:32 PDT 2019; root:xnu-4903.251.3~3/RELEASE_X86_64 x86_64 * **Subsystem**: <!-- Please provide more details below this comment. --> I've created a simple testing framework that runs tests using vm.Script.runInContext(). Now I'm writing tests for code that uses the whatwg URL API. If I use `vm.createContext()`, the created context does not define the URL() constructor. But if I pass in the URL constructor with `vm.createContext({URL})`, then I have a situation where arrays returned by URLSearchParams methods are defined using the Array.prototype object from outside the context, and my tests are trying to compare those to arrays defined inside the context with a different Array.prototype object. So because I have two arrays with different prototypes, `assert.deepStrictEqual()` thinks they are not the same. I'd argue that the underlying bug here is that URL should be automatically defined in newly created contexts without having to be passed in. Or maybe this is a bug in `assert.deepStrictEqual()` and it is stricter than it ought to be in this cross-context situation? In any case, here is an example that reproduces the issue for me: ``` const vm = require('vm'); // URL is not defined inside the context, and I can't require it, so // I need to pass it to the context from outside. But it returns arrays // using the Array class from outside the context. let context = vm.createContext({require, URL, externalArray:A…